Help solving ODE using separation of variables

In summary, the conversation is about simplifying a solution to an ODE, with steps and a hint given. The solution involves integrating and using the properties of logarithms. The final step is to remove the extra factor of 1/3 to match the answer in Maple 10.
  • #1
opticaltempest
135
0
Hello,

Could someone please help me to simplify my solution to my ODE?

Here is the solution I get when I check it using Maple 10,

http://img524.imageshack.us/img524/415/ode2hx.jpg

Here are my steps:

[tex]
\left( {1 + x^3 } \right)\frac{{dy}}{{dx}} - 3x^2 y = 0
[/tex]

[tex]
\left( {1 + x^3 } \right)dy = 3x^2 ydx
[/tex]

[tex]
\int {\frac{1}{y}} dy = \int {\frac{{3x^2 }}{{1 + x^3 }}} dx
[/tex]

Let [tex]u = 1 + x^3 [/tex] then [tex]\frac{{du}}{3} = x^2 dx[/tex]

[tex]
\ln \left| y \right| = \frac{1}{3}\int {\frac{1}{u}} du
[/tex]

[tex]
\ln \left| y \right| = \frac{1}{3}\ln \left| u \right| + C
[/tex]

[tex]
\ln \left| y \right| = \frac{1}{3}\ln \left| {1 + x^3 } \right| + C
[/tex]


How do I simplify this down to match the answer in Maple 10?
 
Last edited by a moderator:
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  • #2
HINTS:

[tex]e^{\ln x} = x[/tex]

[tex]\ln x^p = p \ln x[/tex]
 
  • #3
That 1/3 shouldn't be there. Once that's gone, exp both sides to get the same expression as maple.
 

What is separation of variables?

Separation of variables is a method used to solve ordinary differential equations (ODEs) by separating the dependent and independent variables into individual equations.

How does separation of variables work?

In separation of variables, the ODE is rewritten as a product of two functions, one containing only the dependent variable and the other containing only the independent variable. These two functions are then set equal to a constant and solved separately, before being combined to find the solution to the ODE.

What types of ODEs can be solved using separation of variables?

Separation of variables can be used to solve ODEs with first-order derivatives, as well as some second-order derivatives that can be rewritten as first-order derivatives. It is most commonly used for homogeneous linear ODEs.

Are there any limitations to using separation of variables?

Yes, separation of variables can only be used for certain types of ODEs and may not always yield a solution. It is also not suitable for solving partial differential equations.

What are some tips for using separation of variables to solve ODEs?

It is important to carefully identify the dependent and independent variables and to clearly separate them in the initial equation. Additionally, it may be helpful to try different variable substitutions or rearrangements to simplify the equation before applying the method.

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